Systems incorporating optical fibers are well known and find an ever-increasing variety of applications. Such systems include optical fiber communications systems, medical instruments, copiers, printers, facsimile machines, scanners, optical displays and lighting.
Contemporaneously with the increased use of systems utilizing optical fibers, polymer optical fiber (POF) is being recognized as a cost-effective alternative to conventional glass optical fiber for many of the above-mentioned applications. See for example, F. Suzuki, "Novel Plastic image transmission fiber," Proc. SPIE, 1592, 112-132, (1991); G. Brun, C. Farget, M. Reglat, M. Druetta, J. P. Goure, and J. P. Montheard, "Plastic optical fiber for lateral illumination: chemical studies and optical measurements," in Proc. 4.sup.th International Conf. Plastic Optical Fibers & Applications, Boston, MA, Oct. 17-19, 1995, pp. 187-192; J. Farenc, and P. Destruel, "Illumination, signalisation, and decoration using plastic optical fibers," in Proc. 4th International Conf. Plastic Optical Fibers & Applications, Boston, MA, Oct. 17-19, 1995, pp.203-205; S. Sottini, D. Grando, L. Palchetti, and E. Giorgetti, "Optical fiber-polymer guide coupling by a tapered graded index glass guide," IEEE J. of Quantum Electronics, 31, 174-180 (1995). Among the most frequently cited advantages of using a POF are its fundamental low weight, flexibility, resistance to breaking, low material and connection cost, and immunity to electromagnetic interference.
In many of the applications employing optical fibers, polymer or otherwise, small amounts of light traversing the fiber need to be tapped and subsequently emitted from the fiber. Consequently, a number of prior art methods have been developed for causing optical fibers to emit light from the fiber.
U.S. Pat. No. 4,466,697 discloses a light dispersive optical lightpipe and method of making same. The optical lightpipes are doped in a core region with refractive and/or reflective light scattering particles. When light traversing the lightpipe strikes a particle, it is scattered and some of the scattered light exits the lightpipe through a side. As disclosed in this patent, the light scattering particles are preferably incorporated into the lightpipe during manufacture, by adding light scattering material with the molten core before extruding the material as an optical fiber.
U.S. Pat. No. 5,037,172 discloses a method of manufacturing a reflective notch coupler for an optical fiber. The coupler is formed in an optical fiber by a pair of angled surfaces extending from the cladding of the optical fiber and meeting in the fiber's core to form an indentation in the fiber. One surface of the fiber is reflectively coated and couples light into and out of the core of the optical fiber.
U.S. Pat. No. 5,432,876 discloses an illumination device and optical fibers for use within the illumination device. According to the patentees, an optical fiber is provided with a light emitting region along at least a portion of its length. In the light emitting region, there are constructed a number of optical elements which include reflecting surfaces, at least one of which has a cross sectional area less than that of the fiber. Light traversing the fiber which strikes the reflecting surface is reflected out of the fiber. In order to maintain a substantially uniform output illumination along the light emitting region of the fiber, the morphology, pattern and spacing of the optical elements are varied as desired.
Finally, U.S. patent application Ser. No. 08/667,164 and a subsequent article entitled "Distribution of Light Power and Optical Signals Using Embedded Mirrors Inside Polymer Optical Fibers" by Y. Li and T. Wang (the inventor of the present application), which appeared in IEEE Photonics Technology Letters in October, 1996, there is shown how light may be distributed through side-emitting ports along a polymer optical fiber. The ports include an imbedded mirror region, which is produced by cutting and refilling a portion of the optical fiber.
While these prior-art techniques and devices exist for tapping a light signal conducted by an optical fiber, a continuing need exists for methods and devices which tap and control the emission of light from an optical fiber.